It's the time of year for messing around on boats. The great equaliser in recent boating history, the invention that has made going to sea a possibility for hundreds of thousands of people, is the rigid inflatable, a small boat with a wooden floor and sides of air-filled rubber.

Like all the best designs, it was invented as a matter of necessity when the bottom of an ordinary inflatable dinghy was irreparably holed.

The year was 1964, the place was the newly founded sixth form school, Atlantic College on the Bristol channel, the designers were students led by the indefatigable Admiral Des Hoare, and the only substitute material to hand was a bit of plywood. It was duly glued to the surviving bits of tube, and put to sea.

On the choppy waters off the South Wales coast, it was uncomfortable. But in less than a year it had been modified so that the hull had assumed the V-shape that it still has today. Thanks to the Admiral, the potential for a low-cost, high-performance power boat had been spotted by the RNLI who needed a craft for inshore rescue.

Five years later, after two students built a larger model and came 19th in the round-Britain powerboat race, the RNLI bought the patent for the design from Admiral Hoare for £1. He never cashed the cheque. In the past 40 years the design has been repeatedly modified but the concept is the same. Not everyone appreciates the throaty roar of a large outboard engine driven by a petrolhead disturbing a summer's afternoon – unless it is coming to rescue you.